johnsson



K. E. T. JOHNSSON.

MEANS FOR GRINDING PAHABOLIC SURFACES.

APPLICATION rxLEnMAR. la. |918.

. Patented Dec. 23,1919.

2 SHEETS-SHEET l.

K. E. T. JOHNSSON.

MEANS FOR GRINDING PARABOLIC SURFACES.

APPLICATION FILED MAR. 13| 1918."

Pateted Dec. 23, 1919.

2 SHEETS-SHEET 2.

lill

KNUT E, T. JOHNSSOI', V0]? NEW' YORK, N'. Y.

MEANS FORv GRINDING- PARABOLIC SURFACE'S.

Specification of Letters Patent.

Patented Dec. 23, 1919.

Application filed March 13, 1918. Serial No. 222,252.,

To all whom t may concern." y

Be 1t known that I, KNUT E. T. JOHNS- soN, subject ,of the Klng of Sweden, residing at N ew York city, in :the county of New York and State of New York, have invented new and useful Improvements in Means for Grinding Parabolic Surfaces, of which the following is a specification.

This invention comprises a device which is designedito grind and polish either the convexed orthe concaved surface of a parabolic reflector for use in connection with search lights, head lights or similar light projecting devices.

My invention has for its object to provide a device which will accurately grind and polishthe convexed 4and concaved parabolic surface of a ,reflector of any predeand to accomplish the'above by mechanism which operates automatically when the'required dimensions arey determined upon, and the mechanism is set to correspond with those -dimens1ons, the polishing and grinding mechanism maintaining the correct angle with relation to the surface to be polished at all times during the operation.

My means of accomplishing the foregoing objects may be more readily understood by titl having. reference to the accompanying draw-,

ings which are hereunto annexed, forming parts of this specification, in whichy Figure 1 illustrates a top plan view of the mechanism with parts broken away and partly in section;

lFig. 2 illustrates a side view of a portion of the mechanism being broken away and shown in section;

hig. 3 illustrates an end elevation of the mechanism, the supporting bed being shown in section, and

Fig. 4E illustrates a fragmentary plan view of the redector, the reflector holding mechanism being shown in section similar to the showing in Fig. 1, the position of the parts being shifted by the did'erence in location of the grinding and polishing means. i

The frame or support for the mechanism as shown in this embodiment of the invention may consist of a porting bed similar thereto as identified by number 1 of the drawing, the said bed having a rib 2 to serve as a guide for certain parts of the mechanism whlch will presently appear. Atthe end d designed to hold the reflector a. 1 have face ground .and

ing from it and a a pin or the plate plate lll, the

lathe bedor a sup.-

of the bed 1 is a chuck holding a reconcaved surpolished, but it will be apparentv that when the convexed surface is only illustrated a chuck for Hector which is Ahaving the being ground and polished, a different form of chuck `will have to be employed, these chucks being standard and forming no part of the present invention.

b The chuck is of course to be mounted to is being ground and polished.

As illustrated, the lathe bed is provided wlth -the usual cross feed which slides upon its guide 5, the cross feed being formed witha downwardly extending lug 9 extend-lv ing into a guideway 6, and which has internal threads in which is mounted a feed screw 7. The said feed screw 7 is operated by the usual crank 8 which is mounted on it. Means are provided for clamping the guide rigidly to the bed 1 at different positions of adjustment, the means comprising a plate 11 and upon a bolt 13 which extends downwardly from the guide 5. Mounted upon the lathe bed 1 adjacent the cross feed is va platel 14 which is movable longitudinally of the said bed, the plate 141 having a bolt 15 dependnut 16 mounted thereon, the clamping plate 17 being located intermediate the nut 16 and the lathe bed 1, so

that the plate 14 may be locked in any desired position relative 'to the cross feed.

Extending upwardly from the cross feed 10 is apin or pivot 18 `which is designed to travel on the .line of the directrix while pivot 19 is iixedly mounted upon rabola. Y v

Links or levers 20, 21, 22 and 23 constitute what-might be termed a toggle and the links 20 and 22 have ends pivotedv on the stud 18 which is carried by the cross feed 10 which as stated moves along the line of the directrix, whereas ends of the links 2 1' and 23 are pivoted onthe stud 19 on the position of which is fixed by means of the bolt and the nut and clamping plate '16 and 17 respectively. The end of the link the end of the link 21 remote'from the pin 19 are pivotally connected together on a stud 241 which extends downwardly from a guiding member`26. The end of the stud 1s threaded to engage a nut 24:al by which the 'parts are held in assembled relation. A.

remote from thepin 18 and continuously rotated while the reflector V a nut 12 which is mounted lll located at the focus of the pasimilar construction isemployed for connecting the ends of the links 22 and 23,

this construction being more clearly shown in Fig. 2 as comprising a guide 27 and stud/ which has a nut 25a threaded thereon.

An oscillatable bar 28 is mounted inthe guides 26 and 27 and the said bar has an aperture 28a for the reception of a depending stud 29. The stud 29 is connected by the* bridge plate 30 to the channel arm 30a, said channel arm lbeing an extension of the arm 30b on the yoke 35 and the said arm and channel arm are attached together by screws 38, said channel arm 30a having a longitudinally extending channel 31 .to receive the bar 32 on'which'the Channel arm reciprocates, it being shown in the drawing that v anti-friction balls 33 are interposed between the wall of the channel and the bar' 32.

The bar 32 vconstitutes a support for the f arm- 30b of the yoke -35 andas the cross feed is moved, the yoke 35 may move with relation to the member 32. The bar 32 is supported rigidly with respect to the cross feed 10 by means of thevpost 34 which rises from i.the cross feed and is connected to the said The yoke35 has its a`rms'35a and 25b pro-f A grlndmg Atool 43 is carrledby a shaft 44 journaled in a bearingA 45 carried by the yoke 36 and the said shaft 44 has a pulley or the likeA 46 by which the shaft is turned'. Any

usual means may be employed for prevent-l ing longitudinal movement of 'the shaft in' the bearing as itisfdesir'able to maintainthe relation of the grinding andpolishing. toolY to the axes of the pivots 37 at all times during the operation of the device. Y' It will be. observed from the foregoing that the relation oflparts isA such that the axes of. the pivots 37 areV in vertical alinement and the grinding point of the wheel should be directly in line with the axes of the said pivots, so that when this construction is followed, the relationshipbetween .the

grinding point of the wheel or other polish# 111g means and the parabolic curve of the reflector being ground or polished will be,

automatically maintained at all times by the mechanism hereinbefore set forth. v Although I have shown and described a specific means foraccomplishing particular results such as the means of driving the shaft 44,4it-will be obvious that any suitable means for accomplishing this purpose maybe employed.

` The dnectrx and focus having been irst .It will bases thereo determined, the proper-relationship between the pivots 18.and 19 is established. The power is applied to the lathe and the chuck 3 is rotated. The lever 8 is revolving, thus causing the rotation of the feed screw 7 which moves the cross feed 10 across the lathe' bed 1. It will be apparentthat as this movement is continued, the pivot 18 is brought nearer to the pivot 19 and that this movement will impart an oscillating move ment to the links 20, 21, 22 and 23 which will operate to oscillate the guides 26 and 27 upon the bar 28, the position of which will obviously be affected, causing it to swing upon the pivot 19 until it has assumed the position shown in Fig. 4. This movement, through the medium of the pin 29 and the bridge plate 30, causes the arm 30n of the yoke 35 to slide upon the guide 32 while at the same time motion is imparted to the yoke 36 through the pivot 42 operating upon the link' 40 and arm 39. In this manner, the membersmove the pin 29 until it is directly between and in line with the pivots 18 and 19 at which points it is at the apex of the vparabola and therefore the pivots 37 will be curvature and thatthe point of the grinding f medium will at all times travel on the line arabola.

e noted thatdf a line were drawn from thepivot 18 to the pivot 19, two right angle triangles would be formed on the opposite sides of the bar 28, the links 20 and 21 being hypotenuses of said triangles and the adjacent ortion ofthe bar forming the fl.) In other words, the center line of the barbisects the angle formed by the center lines of the links.

I claim-4 1. In a device of the vcharacter described, a work holder adapted to be rotated, a pivot of a true stationary and in aline with the apex or axis of 'an element to'be worked, a pivot, means for mounting the pivot for movement along the line of the directrix of a parabola and at right angles to the line first menti'oned, a link having one end oscillatable on .the rst mentioned pivot, a link having one end'foscillatable on the second mentioned pivot, and means for pivotally connecting the opposite ends of the links, a reciprocating'. bar, means carried Iby theapex of the links for slidably maintaining the bar on The o eration of the deviceis as'follows:

lines which represent the sides oftriangles of which the links would describe or reprementioned titl naam-s sent the hypotenuses, a slidable member, means tor communicating the motion ot vthe bar to the slidable member, `a support for the slidable member carried by the aforesaid pivot carrying means pivots on the slidable.'

member, a yoke oscillatable on the last mentioned pivots, a tool, means carried bythe yoke for mounting the tool for rotation With its point of contact with tbe Work in a plane with the axis of the last mentioned pivots, and means` for communicating 'the motion of the bar to the said yoke.

2. lln a device of the character described, a bed, a Work holder adapted to be mounted torrotation with relation to the bed, a stationary pivot on the bed in line withthe apex or axis of an element to be carried by the Work holder, across feed movable at right angles to the line of the apex, a link having one end pivotally connected tothe cross feed, a. link oscillatable on the stationary pivot, means for' pivotally connecting the opposite ends of the links, a reciprocating bar, the links for slidably maintaining the bar on lines Which represent the sides of triangles of which the links -Would describe or re resent the hypotenuses, a slidable member, means for communicatin lthe motion ofthe bar to the slidablememi er, a support forV the slidable member carried by the aforesaid pivot carryin means, pivots on the slid able member, a yo e oscillatable on the last pivots, a tool, means carried by the yokegfor mounting the tool for rotation with its point ot contact with the Work in a plane With the axes of the last mentioned pivots, and means for communicating the motion of the bar to said yoke.

3. lin a device of the character described, a bed, a work holder adapted to be mounted for rotation with relation to the bed, a stationary pivot on the bed inline With the apex or axis of an element to be rotated with the work holder, a cross feed movable at right angles to the said line of the apex, a pivot carried by the cross feed, a link having one end oscillatable on the first mentioned pivot, a link having one end oscillatable on the second mentioned pivot, means for means carried by the apex of pivotally connecting the opposite ends ofthe links, a reciprocating bar,.ineans carried by the apices of. the links for slidably 'maintaining the bar on lines which represent the sides of triangles of which the links would ydescribe or represent the hypotenuses, a

slidable member, means for communicating the motion of the barto the slidable member, a su port'for the slidable member, carried by t e aforesaid pivot carryin means, pivots on the slidableV member, a yoiie oscillatable on the last mentioned pivots, a tool, means carried by the yoke for mounting the tool for rotation with its pointof contact with the vWork in a plane with the axis of the last mentioned pivots, and means for communicating the motion of the bar to the said yoke.

4. ln a device of the-character-described,

a Work holder adapted to be rotated, a pivot stationaryv and in a line with the axis of the element to be Worked, a pivot, means for mountin the pivot for movement along the line of tile directrix of a parabola and at right angles to the line of the first mentioned axis, two links, each having an end oscillatable on the first mentioned pivot links oscillatably mounted on the second mentioned pivot, means for pivotallly connecting the first and second mentioned links together in pairs,- by the apices of the lin s for slidably maintaining the bar on lines which represent the sides of triangles of Which the links Would describe or represent the hypotenuses, a slidable member, means for communicating themotion of the bar to the slidable member, a support for the slidable member carried by the said means tor mounting the pivot, a yoke 'oscillatably mounted on the slidable member, means mounted on the yoke for rotatably supporting a tool, the

v relation of parts being such that the operaoif' the tool contacts the Work in al tive point plane With the axis of oscillation, of the'yoke, and means tor communicating the motion of `.the bar to said yoke.

In testimony whereof I aliix my signature.

KNUT E. T. JoHNssoN.

a reciprocatin bar, means carried l 

